Renogy GEL 200ah not lasting more than 2.5 Hours

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surgess asked Sep 24, '22

Renogy GEL 200ah not lasting more than 2.5 Hours

I have a Victron Multiplus 12/3000/120-50 connected to a 200ah Renogy Gel with two + and - 0g wires while running about 16amps the battery only lasts about 2.5 hours before the system says low battery and shuts off. Let the system completly charge to float and still same issue.

I bought a bluetooth dongle to connect to the system to see whats going on and confirmed amps being used I just ordered the MK3 programing unit but not sure if that is the problem.

These are the default settings from the unit so it looks like there are some changes to make but is it that extreme of a differnce I was hoping for at least 8 hours of use.

Any help would be appreciated.

This is what I see after system goes into float.

And this is after a minute or two disconnected from shore power.

Any help would be appreciated still waiting on the MK3 to come in today

battery charging multiplus ve.bus

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Answer 1 · 2022-09-25T01:10:48Z

ludo answered · Sep 25, 2022 at 01:10 AM

How high is your charge current, for the gel battery it shouldn't be more then 20amps.

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surgess commented · Sep 25, 2022 at 05:05 PM

Can I check that without having the MK3?

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surgess commented · Sep 26, 2022 at 12:54 PM

I changed charge current to 20amps let the system drain still same issue

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Answer 2 · 2022-09-25T09:29:04Z

kevgermany answered · Sep 25, 2022 at 09:29 AM

With a load, battery voltage drops quite significantly, if the load is taken off, the voltage will recover quite nicely. Net result is that the low battery voltage disconnect kicks in much earlier than you expect.

Try measuring actual battery voltage with a meter every 15 minutes under load, and as soon as the multiplus cuts out.

One other point... You have a 200Ah battery. 8h at 16A is 128Ah. You shouldn't take it down lower than 50% if you expect a decent service life. Check with the battery maker, but you may find that the 200Ah rating is based on discharge over 20 hours. Loading higher than this (10A) has a lower battery capacity rating, exacerbating your problems.

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nickdb ♦♦ commented · Sep 25, 2022 at 09:52 AM

Specs seem to indicate that 8-hour capacity is nearer 180AH.

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ludo commented · Sep 25, 2022 at 11:15 AM

Sure, but his system shuts down after 2.5 hours, not 8 !

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nickdb ♦♦ ludo commented · Sep 25, 2022 at 11:21 AM

Without a battery voltage/current chart over a representative period it is all guesswork.

Voltage can drop off quite fast as it discharges, so it may not take much, as already said, to make it cutoff.

The suggestion to use a meter to manually check was a good one, in the absence of an alternative.

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kevgermany ♦♦ ludo commented · Sep 26, 2022 at 07:27 AM

I saw the same behaviour on my system. Very early shutdown, traced to battery voltage dropping under load. As soon as load taken off, battery voltage recovers quite quickly, but drops quickly if load reapplied. Low voltage shutdown needs to be set to reflect battery performance under normal system loads.

Also worth remembering that SOC calculations based on battery voltage are really only valid when the system is idle and has been idle for quite some time(i.e. battery voltage stable)

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Answer 3 · 2022-09-26T15:22:09Z

ludo answered · Sep 26, 2022 at 03:22 PM

Yes, a bmv would be helpful, I believe the batteries have been killed with the default charge current of the multiplus.

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kevgermany ♦♦ commented · Sep 26, 2022 at 04:45 PM

Could be, but until we get voltage/time readings from the OP...

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